When building a ventilation system make sure you donât pull
fumes past your face on the way out, as happens with oven hoods
set above a fume source (such as a casting unit). Always test a
ventilation system with soap bubbles or a smoke trail from rope
or cloth to see how it really works.
Charles
Here is an extract from âThe Jewelry Workshop Safety Reportâ
Ventilation
There is a real consensus that ventilation is incredibly
important in having a safe studio. You need it. Remember that it
is dusts, fumes, mists and vapors that cause much damage to
people. Therefore, if you can get the noxious materials away from
you right from the spot where they are generated, that is the
best solution, as long as they are removed completely and are not
immediately sucked back into your building by a wrongly placed
air makeup intake duct.
Dilution ventilation, which is where you open a window next to
you, and another one elsewhere, so that air passes you on its way
out, is used in many shops. Dilution ventilation is not generally
an effective approach. Even materials like rubber cement and some
permanent markers demand adequate ventilation over and above the
dilution type-their solvents can be very toxic (hexane in rubber
cement, for instance).
What we really want most of the time is local ventilation, which
means a sucking device, slot or tube close to the working area
that is generating the dust, mist or fumes that need to be
vented. The book Ventilation: A Practical Guide for Artists,
Craftspeople, and Others in the Arts by Clark, Cutter and McGrane
is a very good starting place, and has specifics on actually
building a ventilation system - I refer you to them for that
kind of as well as to details in McCannâs books.
There are canopies, slotted hoods and âelephant trunkâ types, the
latter a hose with a hood that can be moved to different spots on
a work surface. Local ventilation, very close to the source of
the problem, is the best method of dealing with noxious dusts,
fumes, vapors and so on. Get the bad stuff away as fast as
possible, as close as you can get to the point where you are
generating it. Squirrel cage fans are usually very efficient.
Make sure you donât move air past your face before it leaves, as
with many overhead hoods. Exhaust it safely from your working
space. There are different recommended speeds of air sucking into
your hood for various activities. Examples of different air
velocities barreling into the vent near the work include: 50-100
cubic feet per minute for plating, degreasing, evaporation from
chemical solutions, 100-200 CFM for welding, 500 CFM for
grinding and abrasive use (Stellman and Daum 295). Remember, too,
that the closer you are to a hood opening the more effective it
is. In general fumes and dusts being generated should be as close
as six to eight inches to the mouth of a local suction system.
Some writers take a harder position: âWherever possible,
ventilated processes should be totally enclosedâ (Stellman and
Daum 300).
A fume hood is a good idea if you use chemical solutions and
processes. Sometimes you can buy one at a government surplus
equipment liquidation company. You can build one yourself, but a
professionally built one will probably be of better quality. Use
sheet metal to build it rather than flammable plastic. Have a
ventilation specialist check out your plans before having
anything built. A fume hood should be placed at the back of the
workshop so that if there is an accident the exits are not
blocked. It should also have enough aisle space in front of it,
so that people working in the studio do not interfere with its
use or the air movement into it by moving about near it.
There are other home-made fume hood options as well, but these,
too, should be checked with a specialist before installing them.
Remember that the illusion of safety can induce one to do more
dangerous things than one should. Fume hoods should be tested
every time you use them with a smoke trail or soap bubbles. I had
two students who went to hospital with metal fume fever because
they did not test an extraction system before using it. Remember,
too, that you should exhaust your system properly, not into
areas where the toxic vapors contact people or are even drawn
back into the building by a nearby intake. I remember the horror
I felt when a Japanese friend of mine told me about her
apprenticeship and how her shop would exhaust mercury gilding
fumes from the workshop outside at face height onto a Tokyo
sidewalk.
Ventilation means that air is being sucked out of your
workspace. This air then has to be made up from someplace,
perhaps from the rest of your building or from make-up intakes
placed carefully distant from the ventilation exit point. It is
important to ensure that your make-up air is not bringing in
vehicle exhaust fumes, is not downwind from a chimney that is
putting out toxic fumes, and is otherwise not bringing in
noxious air (Kornberg 111). In large institutions using
ventilation, care has to be taken to âtemperâ (heat up) the
incoming air in cold localities so that the work rooms do not get
too cold. Heat loss and the costs of heating have to be measured
against the health benefits of the ventilation. Me, I will go
with the ventilation and wear a sweater if necessary under my
work clothing.
In general the most effective way of dealing with proper
ventilation and still considering the cost of heating the
workspace is to reduce the amount of air being handled, and to
use it only when it is necessary for a specific task. Use a
low-volume but high-air-speed hood, sort of like the slit of a
vacuum hose. A hood in a slit shape with a small tube behind,
leading to the extraction fan, makes for a high air speed at the
mouth of the slit hood. Use local exhaust ventilation as much as
possible (Qualley 27). McCann says: âVentilation should always be
tried before considering respiratory protectionâ (McCann, HHM
87).
Anytime you can smell a material, solvent or chemical you should
take it as a warning. If a smell bothers you then it is
considered irritating and you should reduce your exposure to it
by changing your procedure or by using local ventilation. âIf you
can smell it, you need ventilationâ (Crumley 128, 130).
Slit ventilation is very effective in jewelry workshops.
Charles Lewton-Brain
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada